Hello World. Browsing through the nutrition facts about a pack of leg quarters I've been wanting to buy, I just had just two quick questions about them (they should be logical, but I can never be too careful):

1. 4 oz. is about one quarter leg, right?
2. When it says edible portion, that means just the skin and the meat, not the bones?

How much of each leg quarter is a serving really varies. I buy some that are close to a pound, and others are less than half that weight. You'll need to use a food scale to be certain. And if you use one, you weigh after cooking. To account for the bone, you can weigh before and after weighing, or estimate.

If you're not used to knowing what four ounces of meat looks like, weighing is your best option, but most people guesstimate. A pack of cards is about the size of four ounces.

Yes, but like Ntombi said, it's best to weigh after cooking as you'll get a more accurate count that way.
Meats lose a lot of weight with cooking. Fat renders, and some supermarkets infuse chicken with water or broth to increase weight (and therefore, price).